Solid State Ionics最新文献

We combine ⁷Li NMR relaxometry and diffusometry with electrochemical impedance spectroscopy to unravel the mechanisms for the dynamics and transport of lithium ions in the lithium-deficient and halide-rich argyrodite Li_5.5PS_4.5Cl_1.5. In particular, we determine the effects of heat treatment on the cooperativity, heterogeneity, and subdiffusion of lithium ion motion. We find that heat treatment results in an enhancement of the dc conductivity by a factor of six to a high room-temperature value of ${\sigma }_{\mathrm{dc}}=14.9$ mScm⁻¹, whereas the change of the ⁷Li NMR self-diffusion coefficients $D$ is considerably smaller. Accordingly, heat-treated Li_5.5PS_4.5Cl_1.5 shows a very small Haven ration of $H_R=0.13$ indicative of a high cooperativity of lithium ion dynamics. Moreover, after heat treatment, the collective correlation factor $f_I$ becomes very small, which is related to a strongly reduced relevance of subdiffusive lithium ion dynamics. However, heat treatment does not affect the activation energies, which are in the range $E_a=0.34-0.40$ eV for the dc conductivity ${\sigma }_{\mathrm{dc}}$, the diffusion coefficient $D$ and also for the jump correlation time $\tau$. ⁷Li NMR field-cycling relaxometry allows for a characterization of the lithium ion jumps based on a frequency-dependent dynamical susceptibility. We find that the susceptibility peak has a strongly asymmetric shape with a hardly broadened low-frequency flank and a strongly broadened high-frequency flank, reflecting a characteristic heterogeneity of the lithium ion dynamics, which derives from the specific cage-like arrangement of the lithium sites and the resulting difference in the rates of intra-cage and inter-cage jumps. Considering further the anion disorder in the crystal lattice, we propose that heat treatment facilitates cooperative inter-cage jumps, suppressing localized subdiffusive motion and enabling long-range ion transport along percolating pathways.

The La_xSr_1-xCo_yFe_1-yO_3-δ family of mixed conducting materials shows high electron- and oxygen ion conductivity, together with an appreciable catalytic activity for dissociation of ambient oxygen. These properties are of importance for solid oxide fuel cells. In this family of compounds, La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) has been well-studied, both fundamentally and in actual applications. The related composition, La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF6482) has received much less attention despite its higher electronic and ionic conductivity. Literature results show for this composition sometimes rather conflicting results.

The finegrained (100-150 nm) porous LSCF6482 electrodes show at higher temperatures a low-frequency dispersion, in the frequency range of ∼0.01–10 Hz. This dispersion is the result of gas phase diffusion limitation (GDL) coupled to the redox behavior of the mixed conducting LSCF6482. Applying a dense, thin layer of LSCF6482 between electrolyte and porous electrode improves the electrode properties, as it removes the ‘bottle neck’ for charge transfer of surface adsorbed oxygen moieties.

Mixing Gd-doped cerium oxide, Ce_0.9Gd_0.1O_1.95 (CGO) with LSCF6482 in a porous electrode structure improves the electrode properties significantly as CGO has apparently a better catalytic activity for oxygen dissociation. The mid-frequency capacitance, C_mid, is assigned to surface charge, i.e. adsorbed O_ad⁻ species. The introduction of CGO in the electrode appears to shift the dissociative adsorption of oxygen from the LSCF surface to the catalytically more active CGO surface. The significantly lower area specific resistance (ASR) is, however, strongly dominated by a larger GDL contribution at temperatures above ∼600 °C.

The separator is crucial to the performance and safety of the battery. This study prepared a polypropylene (PP) /solid electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) /SiO₂ composite separator (PP/LATP/SiO₂). The experimental results demonstrate significant enhancements in the electrolyte wettability and thermal stability of the separator. Furthermore, the lithium-ion transference number ($t^{+}$) has been raised from 0.22 to 0.56. In electrochemical performance tests, the lithium symmetric battery assembled with the PP/LATP/SiO₂ composite separator exhibits an exceptionally long cycle life, sustaining stable cycling for 900 h at a current density of 0.5 mA cm⁻². This composite separator, combining the solid electrolyte and SiO₂ layer, effectively facilitates lithium-ion transport and reduces the occurrence of electrode side reactions, thereby enhancing the performance and safety of the battery.

The dawn of bimetallic transition metal nitrides has attracted considerable interest as battery grade electrode material for potential energy storage applications. In addition, it is essential to investigate binder-free processes to improve the performance of the fabricated electrodes. In this study, binder-free tungsten‑titanium nitrides (W-TiN) are deposited through RF/DC magnetron co-sputtering onto the conducting nickel foam (NF). SEM, EDX and X-ray diffraction are exploited to investigate surface morphology, elemental composition, and structural properties of sputtered materials. The W-TiN electrodes are characterized through electrochemical investigation in half-cell configuration. The tested W-TiN electrode is further utilized with activated carbon (AC) electrode to develop hybrid supercapacitor device W-TiN//AC. The hybrid device revealed a maximum energy density (E_s) of 88.8 Wh/kg and power density (P_s) 1700 W /kg. To further understand the mechanism of hybrid devices, the capacitive and diffusive contributions are computed using linear and quadradic models. This study provides a new direction to integrate co-sputtered binder-free electrode materials and devices for large scale production of advanced hybrid energy storage devices.

Polyethylene oxide (PEO) is considered as the most promising and widely studies polymer matrix. However, its practical application is limited for its low ionic conductivity at room temperature. Here, a novel fluorinated branched (2,2,2-Trifluoroethyl methacrylate (TFEMA)) ether polymer (PFP) was synthesized through thiol-Michael addition click reaction and blended with PEO to obtained PEO-based polymer electrolyte. The introduction of PFP could reduce the crystallinity and hinder the migration of anions, resulting in a double increase in ionic conductivity and lithium-ion transference number. More importantly, the symmetric Li/Li employing blended polymer shows stable cycle more than 1700 h and the Li/LiFePO₄ cell shows the superior performance of both cycling and rating at 60 °C. Even at lower temperature (28 °C), the Li/LiFePO₄ cell exhibits encouraging cycling performance with 88.6% capacity retention at 0.2C after 100 cycles. This study provides a novel strategy for structural design and synthesis progress of solid polymer electrolyte.

Due to plenty of potassium in the Earth's crust, potentially high energy density, high conductivity and fast ionic diffusion, potassium ion batteries (PIBs) are expected as promising and competitive alternatives to lithium-ion batteries (LIBs). However, in order to obtain high-performance potassium ion batteries, it is crucial to find suitable anode materials. Herein, from first principles methods based on DFT, we have investigated the possibility of a new two-dimensional material, penta-germagraphene (denoted as P-Ge₂C₄) obtained by doping Ge atoms in penta-graphene, as anode materials for PIBs. The theoretical specific capacity is 554.8 mA h g⁻¹. The intercalation potentials between 0.1 and 0.65 V are suitable for use in batteries. The metallic electronic structures of P-Ge₂C₄ adsorbed K-ions and relatively small of diffusion energy barriers ensure good rate performance. The results show that two-Dimensional P-Ge₂C₄ can be applied as an anode material for PIBs with good performance.

In the present work, we studied the features of phase formation in mechanically activated Ti + Al powder mixture at various heating rates for the first time. The study was carried out using high-resolution diffractometry method which made it possible to study the processes of phase formation in situ at any stage of heating. It was established that ignition of the activated mixture can be initiated in the solid phase with an extremely low content of reaction products formed at the preheating stage. An increase in the heating rate leads to a decrease in the average burning rate and an increase in the ignition temperature. At high heating rates, the ignition is initiated in the presence of a liquid phase when the ignition temperatures are close to the melting temperature of aluminum. In this case, the content of reaction products formed during preheating stage is relatively high. It was found that the all main compounds presented in the equilibrium diagram of Ti-Al system are synthesized in parallel. The content of phases in the reaction products depends on the heating rate.

In this study, we synthesized co-doped Li_6.25Al_0.25La_3-yNd_yZr₂O₁₂ (LALNZO) solid-state electrolytes with varying Nd contents to investigate the influence Nd plays on phase evolution, microstructure, and lithium-ion conductivity. It was found that incorporating Nd ions into the lattice reduced bulk resistance by controlling Li⁺ concentration. However, X-ray diffraction analysis revealed that excessive Nd content led to the formation of Nd₂O₃, which negatively impacted ion transport and increased grain boundary resistance. It is noteworthy that the LALNZO (y = 0.2) ceramic exhibited outstanding performance, with 94% relative density, and ionic conductivity of 4.7 × 10⁻⁴ S/cm. The activation energy was 0.32 eV. Further, Li_6.25Al_0.25La_2.8Nd_0.2Zr₂O₁₂ was able to demonstrate a stable capacity of 103 mA.h. g⁻¹ after 50 cycles at a current density of 0.1C when used as an electrolyte in lithium-ion batteries. The findings of this study provide valuable insights for developing advanced solid-state electrolytes for lithium-ion batteries.

Aqueous zinc-ion battery (AZIB) is one of the most promising candidates for large-scale energy storage, so it is critical to explore low-cost cathode materials with practical prospects. Iron-based phosphate cathodes have been shown to be very important in lithium/sodium-ion batteries, but have rarely been applied in AZIBs. Herein, hydrated zinc iron phosphate Zn₂Fe(PO₄)₂·xH₂O (ZFP) is first proposed as potential cathode material for AZIBs due to its advantage of layered structure with lubricative interlayer water. Carbon coated Zn₂Fe(PO₄)₂·xH₂O (ZFP@C) can be prepared by using a liquid-phase method combined with a hydrothermal process. Both the specific capacity and rate ability of ZFP@C are more superior than those of the raw ZFP. After 25 cycles of electrochemical activation, the ZFP@C cathode delivers a peak capacity of 137 mAh g⁻¹ with two charge and discharge platforms at 1.82 V/1.89 V and 0.65 V/0.26 V vs. Zn²⁺/Zn, respectively. Finally, it can be proved that the ZFP@C cathode smoothly experiences Zn²⁺ extraction-intercalation reaction in the bulk, and the conversion reaction to Zn₃(PO₄)₂·xH₂O and Fe(OH)₂ from the surface. We believe that these findings will open the application of iron-based phosphate as a kind of low-cost cathode materials for rechargeable AZIBs.

Ruddlesden – Popper phases are promising materials for solid oxide fuel cell/electrolyzer air electrodes, oxygen separation membranes and other electrochemical devices due to their high oxygen mobility provided by a cooperative mechanism of oxygen migration involving both regular and highly-mobile interstitial oxygen. This work aims at studying structural, surface and oxygen transport properties of Sm-doped Nd nickelates sintered in a furnace at the temperatures in the range of 800–1250 °C and using electron beams at the temperatures in the range of 1150–1250 °C. Nd_2-xSm_xNiO_4+δ, x = 0.2 and 0.4 are synthesized by a modified Pechini technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed isotope exchange of oxygen with C¹⁸O₂ in a flow reactor. The phase composition studies show the ability to obtain single-phase materials at certain sintering conditions. Nd/Sm ratio on the surface is close to stoichiometric one, while (Nd + Sm)/Ni ratio on the surface is below stoichiometric. Such materials possess a high oxygen mobility (D^⁎ up to ∼10⁻⁷ cm²/s at 700 °C).